Ammunition primer composition for small arms

ABSTRACT

A heavy-metal free primer composition consisting essentially of potassium dinitrobenzofuroxane as a primary explosive, diazodinitrophenol as a secondary sensitization explosive, and an inert sensitizer is disclosed. The preferred mix is comprised of 50% of potassium dinitrobenzofuroxane, 30% of diazodinitrophenol and 20% of ceramics powder as the inert sensitizer. This composition has sufficient sensitivity, good ballistic properties for all types of cartridges and very strong stability in high temperature and high humidity conditions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from provisional patent application 60/482,643.

FIELD OF THE INVENTION

The present invention relates to ammunition primers, namely to the percussion pyrotechnical compositions for small arms ammunition primers.

BACKGROUND OF THE INVENTION

At present, there is a biological and environmental problem before designers of ammunition. The problem is that the components in ammunition primers are harmful to people and nature. These components are especially toxic when shooting in small areas and enclosed premises, including indoor shooting galleries. The solution requires a significant reduction in the use of these harmful components.

The current technology for percussion pyrotechnical compositions (“PCC”) includes a combination of mercury fulminate (Hg(ONC)₂), potassium chlorate (KCLO₃) and antimony sulfide (Sb₂S₃). However, this composition is not ideal since its combustion is highly corrosive on the gun barrel.

A common problem with PCC is the presence of heavy metals, including mercury and lead, in the chemical compositions. These compositions of heavy metal compounds cause concentrations in the air many times higher than the Maximum Allowable Concentration (“MAC”) when used in indoor shooting galleries. These elements and their compounds are formed after PCC burn when shooting indoors.

A number of developments and patents have been identified which provide relatively pure (clean burning) PCC. These compounds use diazodinitrophenol; however, analysis of these compositions has shown that they have a number of essential deficiencies, including an unsatisfactory stability of ignition.

As an example, the PCC disclosed in U.S. Pat. No. 4,675,059 contains (% mass): diazodinitrophenol (40%), tetrazene (10%), manganese dioxide (30%), and glass (20%). This composition is not ideal as it has a low force and a low temperature of burning. This does not allow the PCC to achieve the stable ignition of charges and required ballistic characteristics of small arms centerfire ammunition. Moreover, manganese dioxide has a higher specific gravity than other mixture components, which results in stratification or separation of the PCC mixture during storage. Consequently, a reliable and stable primer is not provided. Furthermore, it is not ideal since it does not have the required ballistic characteristics of small arms centerfire ammunition. Additionally, the presence of the tetrazene causes low temperature and moisture resistance.

Other technology, including U.S. Pat. No. 4,963,201 and U.S. Pat. No. 5,993,577, has combined tetrazene with oxidizer salts such as strontium nitrate and potassium nitrate. This combination results in high hygroscopic properties and low thermostability and low moisture resistance.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a new composition for primers, which is free of lead and heavy metals, and yet functions at least equally effectively as primers that contain lead and heavy metals. Despite the fact that many attempts have been made with various heavy-metal free (“HMF”) primer compositions, it appears that the most commercially feasible non-corrosive primer composition heretofore developed for cartridges has been the combination of lead styphnate and tetrazene as the primary explosive. This is true despite the fact that the by-products of firing such a composition include lead, which is considered toxic and, hence, such compositions are widely recognized as undesirable.

The present invention is a heavy-metal free primer composition consisting essentially of potassium dinitrobenzofuroxane as a primary explosive, diazodinitrophenol as a secondary sensitization explosive, and an inert sensitizer. The preferred mix is comprised of 50% of potassium dinitrobenzofuroxane, 30% of diazodinitrophenol and 20% of ceramics powder as the inert sensitizer. This composition has sufficient sensitivity, good ballistic properties for all types of the cartridges, and very strong stability in high temperature and high humidity conditions.

BRIEF DESCRIPTION OF THE TABLES

Table 1 shows the ratio of components of the disclosed composition by percent of mass.

Table 2 details the results of ballistic tests of the 5.45×39-mm cartridges with the new primer composition in comparison with the primer composition disclosed in Russian patent RU 2175652 (identified as “Prototype”). Tests are made at temperatures of cartridges +20° C., +50° C., and −50° C.

Table 3 displays times to ignition, peak pressure and peak ignition in the same range of temperatures.

Table 4 details the results of ballistic tests of the new primer composition with changes to the percent mass of potassium dinitrobenzofuroxane.

DETAILED DESCRIPTION

According to the disclosure in Russian patent RU 2175652, incorporated herein by reference, which is a primer composition containing (% of weights): lead styphnate (60-75%), diazodinitrophenol (10-20%), and inert sensitizer (15-20%), the test primers have shown good results when checked for stability of the ballistic characteristics in a range of temperatures from −15° C. up to +50° C., high thermostability and moisture resistance. The increased time of a shot at negative temperatures is a problem of this composition. At temperatures of a −50° C., hang fires and misfires were observed. Additionally, this composition is not free of heavy metals.

The present invention provides an improvement over RU 2175652. It demonstrates stability of the ballistic characteristics and an increase of the reliability of ignition of a propellant charge in a range of temperatures +50° C. to −50° C. as well as preservation of high thermo and moisture resistance. Moreover, it is a non-corrosive and HMF primer composition.

The components of present composition are diazodinitrophenol, potassium dinitrobenzofuroxane and inert sensitizer (ceramics powder). Components are in the ratio, % of mass: TABLE 1 Component % of mass Diazodinitrophenol 20-40 Potassium dinitrobenzofuroxane 30-70 Inert sensitizer (ceramics powder) 15-25

For safety reasons, when dry mixing and pressing, it is advantageous to add small quantities of graphite powder (up to 0.3%) and silica gel dust (up to 0.1%).

The results of the new primary composition tests are given in the tables 2-4.

The advantages of the new primer composition in comparison with previous analogues are evident. Table 2 shows the following advantages: (i) the speed of bullets with the new primer composition is faster, (ii) the dispersion speed of the bullet V25 (25 m from barrel) is reduced, and (iii) there is less deviation in the dispersion speed of the bullet and maximum pressure in the barrel (V25 and Pmax) when the temperature is between +50° C. to −50° C. TABLE 2 Powder ⁴Dis- SF033fl Tem- ¹Bullet ²Dis- persion mass perature speed, persion ³Pmax, Sp_(max,) Primer (gram) ° C. V₂₅, m/s Sv₂₅, m/s at at New 1.36 20 889 2.8 2862 70 New 1.36 50 891 1.6 2938 41 New 1.36 −50 845 6.3 2716 92 Prototype 1.36 20 873 6.1 2802 94 Prototype 1.36 50 882 2.5 2969 74 Prototype 1.36 −50 819 10.1 2594 103 ¹Bullet speed V25: Velocity measured 25 meters from the barrel ²Dispersion SV25, m/s: Variation in Velocity measured in meters per second ³Pmax at: Peak pressure in atmospheres (one atmosphere is 14.7 psi [pounds per square inch]) ⁴Dispersion SPmax: Variation in maximum pressure measured in atmospheres

As shown in table 3, the advantages of the new primer composition include: (i) the ignition time (the time between the firing pin impact and ignition of the powder) is reduced, (ii) the time to achieve the maximum pressure in the barrel is reduced, (iii) the shot time (the total time from firing pin impact to peak ignition of the powder) is reduced and (iv) there are no hang fire episodes (an abnormal length of time to reach peak pressure) at a temperature of −50° C. as compared to 4 out of 10 hang fires with the prototype. TABLE 3 Powder SF033fl ³P max ⁵Shot ⁶Long- mass Temp. ¹Ignition ²Sign, time, ⁴Stp_(max) time, time Primer (gram) ° C. time, ms ms ms ms ms Shot New 1.36 20 0.16 0.017 0.44 0.023 1.20 0 New 1.36 50 0.14 0.010 0.39 0.018 1.11 0 New 1.36 −50 0.18 0.019 0.51 0.027 1.31 0 Prototype 1.36 20 0.17 0.026 0.52 0.028 1.32 0 Prototype 1.36 50 0.15 0.019 0.41 0.022 1.19 0 Prototype 1.36 −50 0.25 0.063 0.67 0.081 1.74 4 ¹Ignition Time: Time between the firing pin impact and ignition of the powder in milliseconds ²Sign ms: Variation in the ignition time ³Pmax Time: Time from ignition to reach peak pressure ⁴Stpmax ms: Variation of Pmax Time ⁵Shot Time: Total time from firing pin impact to peak ignition of the powder. ⁶Long Time Shot: Abnormal length of time to reach peak pressure (known as “hang fire” in standard US parlance, it is detrimental to accuracy, safety and reliability, especially in full automatic firearms)

As shown in table 4, the percentage mass of potassium dinitrobenzofuroxane affects the ballistic characteristics. The purpose of the test is to show that performance deteriorates with either too much or too little compound. The optimal range of percentage mass of potassium dinitrobenzofuroxane is between 30% and 70%. A percentage mass of potassium dinitrobenzofuroxane outside this range leads to a decrease in the bullet speed characteristics and an increase in the time of a shot. TABLE 4 potassium Powder Bullet dinitrobenzof SF033fl speed, ⁴Ignition uroxane, mass V₂₅, ¹Sv₂₅, ²Pmax, ³Sp_(max,) time, % mass (gram) m/s m/s at at ms 28 1.36 869 8.15 2804 131 0.305 50 1.36 887 2.45 2854 71 0.156 72 1.36 874 6.59 2918 81 0.234 ¹Sv₂₅, m/s: Variation in Velocity measured in meters per second ²Pmax at: is the peak pressure in atmospheres. One atmosphere is 14.7 psi (pounds per square inch) ³SPmax: Variation in maximum pressure measured in atmospheres ⁴Ignition Time: This is in milliseconds and is the time between the firing pin impact and ignition of the powder.

The range of acceptable percentage of inert sensitizer was established using a standard sensitivity test, commonly known as a Drop Test, approved by the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI).

Tests show that primers with 15% sensitizer show a 3% misfire rate at a drop height of 24 centimeters. This means that the primer is not sensitive enough as the normal requirement is 0% misfire at this height. Tests at the standard 10 centimeter drop height show that primers with 25% sensitizer show a 5% firing rate. This means the primer is too sensitive as the standard is 0% firing rate at the 10 centimeter height. In addition, increasing the sensitizer beyond 25% produces dangerous/excessive primer pocket pressures and improper powder ignition. Therefore, the optimal range of sensitizer is between 15% and 25%.

Use of the new, non-corrosive, heavy-metal-free, high thermostable and moisture-resistant primer composition provides reliable functioning of cartridges in a range of temperatures +50° C. to −50° C. Also, the dispersion of the ballistic characteristics is much better in comparison with existing analogues. 

1. A percussion primer mixture for use in ammunition comprising: diazodinitrophenol; potassium salt of dinitrobenzofuroxane (potassium dinitrobenzofuroxane); and an inert sensitizer.
 2. The primer mixture according to claim 1, having ceramics powder as the inert sensitizer.
 3. The primer mixture according to claim 1, having from 20 to 40 percent by weight of said diazodinitrophenol, 30 to 70 percent by weight of said potassium dinitrobenzofuroxane, and 15 to 25 percent by weight of said inert sensitizer.
 4. The primer mixture according to claim 3, having ceramics powder as the inert sensitizer.
 5. The primer mixture according to claim 3, having a 30 percent by weight of said diazodinitrophenol.
 6. The primer mixture according to claim 3, having a 50 percent by weight of said potassium dinitrobenzofuroxane.
 7. The primer mixture according to claim 3, having a 20 percent by weight of said inert sensitizer.
 8. The primer mixture according to claim 7, having ceramics powder as the inert sensitizer.
 9. The primer mixture according to claim 3, having 30 percent by weight of said diazodinitrophenol, 50 percent by weight of said potassium dinitrobenzofuroxane, and 20 percent by weight of said inert sensitizer.
 10. The primer mixture according to claim 9, having ceramics powder as the inert sensitizer.
 11. A percussion primer mixture for use in ammunition comprising: diazodinitrophenol; potassium salt of dinitrobenzofuroxane (potassium dinitrobenzofuroxane); an inert sensitizer; graphite powder; and silica gel dust.
 12. The primer mixture according to claim 11, having up to 0.3 percent by weight of said graphite powder and up to 0.1 percent by weight of said silica gel dust. 